Niemals mit dem Teleskop in oder in die Nähe der Sonne blicken:
E
rblindungsgEfahr
!
17
MAINTENANCE
screws and, if necessary, by loosening the central screw located in the
plastic housing of the mirror.
As described above, the 4 collimation screws (Fig. 31b) in the plastic hou-
sing of the secondary mirror are used for two different adjustments proce-
dures being possible during the collimation.
IMPORTANT NOTE:
Never tighten the 4 collimation screws (Fig. 31b) with heavy force above
their normal stop. Never unscrew the collimation screws more than two full
turns counterclockwise (no more than two full turns in the loosening positi-
on). Otherwise the secondary mirror could loosen in its holder. You will pro-
bably find out very quickly that these adjustments have to be made very
carefully. Normally, half a turn is sufficient to achieve the desired result.
3. If the reflection of the secondary mirror is not exactly in the center of the
primary mirror, adjust the primary mirror with the 3 collimation screws
located at the bottom of the primary mirror.
NOTE:
There are six screws on the primary mirror cell (Fig. 31c). The three corru-
gated knobs are collimation screws and the 3 slightly smaller screws are
the so-called counter screws. These will hold the primary mirror in position.
These will hold the primary mirror in position. These counter screws must
be slightly loosened so that you can turn the collimation screws. It will pro-
bably take you some time to get a feel for which of the collimation screws
will change the image as desired.
4. Now perform the test on a star to verify the correctness of steps 1 to 3.
Using a standard eyepiece (20-26mm), point the telescope at a reaso-
nably bright star (2nd or 3rd grade magnification) and position this star
centrally in the field of view of the main telescope.
5. Slowly “move” the image out of focus until you see several circles
around the center of the star. If steps 1 to 3 are performed correctly, you
will see concentric circles (centered to each other) (1, Fig. 32).
If the device is not carefully collimated, you will discover eccentric circles
(2, Fig. 32). Adjust the three collimation screws on the primary mirror hou-
sing until the circles inside and outside the focus are concentric.
It is only important that at the end of the primary mirror collimation the
counter screws are tightened one after the other with a lot of feeling for
several times. Because they now hold the primary mirror tilt-free in the
optimally determined position in the primary mirror cell. Always check the
collimation image (Fig. 32) (also called diffraction pattern).
TIP:
Alternatively, instead of a bright star, you can conveniently perform the
collimation with an alignment laser (optionally available).
Summarized again:
The four adjustment screws on the plastic housing
of the secondary mirror change its tilt angle so that it is correctly centered
in the middle of the eyepiece extension tube and the primary mirror also
appears centered when looking into the eyepiece extension. The three thi-
cker collimation screws on the primary mirror change its tilt angle so that it
reflects the light directly into the center of the eyepiece extension tube.
TIP:
A large number of instructions for adjusting/collimating Newtonian
telescopes can be found, e.g. in the Internet or in reference books.
Checking the optics
Some notes on the so-called "flashlight test":
If you shine a flashlight or an even more powerful light source into the
telescope’s optical tube, you might find something that looks like scratches
or dark or light spots, or even uneven varnish, depending on the angle
of the light and the observer's point of view. This could possibly give the
impression of poor optical quality. The effect of these phenomena on the
optical quality can only be proven with a very large physical measurement
effort and do not limit the function and quality of the high quality optics in
the night sky in any way and do not represent a justified defect for a com-
plaint. They can only be detected when a light source that is much more
Fig. 31b: The four collimation screws
in the secondary mirror housing
Fig. 32: correct (1) and incorrect (2)
collimation.
1
2
Fig. 31c: The six collimation screws
on the underside of the primary
mirror cell
Adjustment screw
(larger)
Locking screw
(smaller)
